Try to avoid truncation of the message in wxMSW wxMessageDialog.

Try to avoid truncation of the message in wxMSW wxMessageDialog.

Use (documented but undefined) TDF_SIZE_TO_CONTENT flag under Windows Vista/7
to reduce the chance that Windows truncates or ellipsizes the message text if
it can't wrap it.

Truncation can still happen for very long words but there doesn't seem to be
any drawbacks to using TDF_SIZE_TO_CONTENT and it does avoid truncation in at
least some cases.

This also improves the situation for wxRichMessageDialog and wxProgressDialog.

Closes #13843.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70409 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775